带加劲环埋藏式压力钢管的抗外压稳定性分析

水电站压力钢管作为一种薄壳结构,在承受外压时易发生压屈而失稳,成为某些水电站压力管道钢衬设计的控制因素.目前规范采用明管抗外压的米赛斯公式计算埋藏式加劲环压力钢管的临界外压,将外包混凝土衬砌对管壁的径向约束作用作为安全储备,安全系数略予降低.为量化这种必然使钢管临界外压增大的混凝土衬砌径向约束作用,首先利用非线性屈曲分析按明管定量分析加劲环式压力钢管的临界外压,进而再通过在外包混凝土衬砌和钢衬间设置接触单元考虑混凝土衬砌对管壁的径向约束作用,按埋管分析加劲环式压力钢管的临界外压,然后与按米赛斯公式和赖华金等所推导的公式计算的临界外压进行对比.表明即使混凝土衬砌和钢管间有均匀分布的缝隙,外包混凝土衬砌的径向约束作用也会使环间管壁的临界屈曲外压明显提高,提高幅度可高达50%以上.

Buckling Capacity Analysis on Embedded Steel Penstock with Stiffener Ring

The steel penstock at hydroelectric station,as a kind of thin shell structure,encounters bucking failure easily under external pressure,which has become the control factor in the design.At present,Mises Formula is adopted to calculate the critical external pressure for the embedded steel penstock in China and America,regarding radial restriction of lining to the pipe shell as safety richness.In the paper,in order to quantitate the radial restriction action which inevitably strengthens the buckling capacity of embedded steel penstock,nonlinear buckling analysis is utilized to simulate penstock with stiffener ring as exposed penstock.Secondly,embedded penstock through set contact pair between lining and the pipe shell is also analyzed.Thirdly,the results by Mises Formula aiming at exposed penstock and those by some other formula deduced by Lai Huajing,which concerns the radial restriction of concrete lining to the steel penstock,are contrasted.At last,the changes of critical external pressure with the seam between penstock and lining are discussed.The results indicate that the restriction action of surrounding concrete lining to the deformation of steel penstock can still increase critical external pressure by 50 percent upwards even taking the initial seam between lining and the penstock into account.